The x-ray edge in alkali metals and alloys, an ab-initio study

Norm conserving pseudopotentials are implemented in the Hartree Fock formalism to study the local electronic response to X-Ray absorption in alkali metals and alloys. The pseudopotentials are tested in a variety of environments and results are compared to full core Hartree Fock results and experiment. It is found that this methodology reproduces experimental results as accurately as the full core Hartree Fock theory. Correlation corrections are included using many body Raleigh Schrodinger perturbation theory. The local absorption spectra of lithium, sodium and potassium are investigated. Accurate excitation energies are obtained for these metals and dilute alloys of potassium and rubidium in lithium. We find that the response of the local valence band qualitatively confirms the theory of Mahan, Nozieres and De Dominicis and quantitatively conflicts with the recently proposed theory of Flynn et al.U of I OnlyThesi